An optical disc has a wobble pregroove which continues in a circumferential direction of the optical disc and wobbles in a radial direction of the optical disc such that the wobble pregroove meanders around a mean center line of meandering. The external controller is preferably further configured to transmit identification information to the implantable electrode for secured information exchange. If the change in terrain exceeds a threshold, the controller generates an alert command signal. The record carrier further exhibits second variations caused by variations associated with the information marks.